In a laptop computer (hereinafter, called a “laptop PC”) or other portable computing device that a user can carry around, protecting the portable computing device from an impact when a user accidentally drops it while carrying it or operating it is a critical issue. In particular, a magnetic disk unit which is commonly used as a storage device in this type of portable computing device is vulnerable to impacts and vibrations because of its structure. It is therefore desirable to provide an effective protecting means for the magnetic disk unit.
A magnetic disk unit reads or writes data by causing a magnetic head to seek over a rotating magnetic disk. If the magnetic head collides with the magnetic disk upon an impact or vibration, the magnetic disk may be damaged, making part or all of the data unrecoverable. Some portable computing devices with magnetic disk units are equipped with a hard disk active protection system (APS) which detects vibrations and others by using an acceleration sensor or the like and, when predicting an occurrence of a severe impact on the portable computing device, makes the magnetic head retracted from above the magnetic disk, thereby improving the shock-proof properties of the magnetic disk unit.
A laptop PC is usually used at a relatively stable place, such as on a desktop or laptop. When the APS predicts the occurrence of an impact, it often leads to dropping of the laptop PC. It is therefore effective to retract the magnetic head.
In contrast, a tablet computer (hereinafter, called a “tablet PC”) is often used while being held with a hand. In this state, the computer suffers small vibrations and tilts repetitively.
In the case where the APS is applied to a tablet PC as in the case of a laptop PC, the possibility cannot be ruled out that a vibration or tilt of the tablet PC that would not actually lead to dropping of the PC is detected and the magnetic head is retracted unnecessarily. If the APS makes the magnetic head retracted from above the magnetic disk each time a vibration or the like occurs in the tablet PC, it will rather impair the practical usability of the tablet PC.